What is myofascial pain?
Myofascial pain syndrome (MPS) is quite possibly one of the most prevalent, yet poorly defined pain syndromes in the general population. Nearly all of us will experience muscular pain at some time or another due to direct muscle trauma, injury, overuse, or an acute strain. Typically the pain will resolve within a few weeks, however, resolution of this acute muscular pain is not always sufficient and in many cases, pain may become chronic in nature.
The medical community continues to debate the specific pathophysiology and diagnostic criteria for MPS, as well as the existence of this pain syndrome at all. As a consumer, you may encounter differing medical opinions and recommended treatments based on the provider’s interpretation of extensive, yet inadequate research studies. While the traditional understanding of MPS is based on the presence of myofascial trigger points (MTrPs), the diagnostic criteria has previously been imprecise.
The traditional diagnosis of MPS is based on the work of Travell and Simons with identification of characteristic a hypersensitive nodule within a tender, taut, palpable band of muscle called a myofascial trigger point (MTrP). For many years, this theory has prevailed, yet has recently become the subject of considerable debate and scrutiny.
Only in the last year (2017) has an international consensus involving 60 experts from 12 countries come up with a standardized definition for MTrPs. The good news is that this will allow for improved consensus on diagnosis for future research studies. Unfortunately, since considerable variability existed prior to this consensus, the existing research studies are difficult to interpret and large meta-analyses may be useless.
Interestingly, MTrPs can be present in asymptomatic (having no symptoms of pain) individuals and are therefore not always associated with pain. Likewise, some individuals who present with symptoms of myofascial pain do not show evidence of MTrPs. Based on these variable clinical presentations, it remains unclear if the MTrP is a causal or pathogenic finding in MPS, however it continues to be central to our understanding of MPS.
And while the majority of medical decision making has been based on the presence of MTrPs in MPS, there may be additional pathology at both the peripheral (in the muscle) and central (in the brain and spinal cord) levels. Within the muscle, nociceptors (receptors that sense painful stimuli) may become overly activated by neuroactive substances (e.g. bradykinin, substance P, serotonin) that are released in response to increased metabolic demands and compressed blood supply that result from sustained muscle contraction due to abnormal release of acetylcholine (ACh). Animal and human studies support the evolving theory that muscle pain may be exacerbated by muscle fatigue due to release of metabolites that cause changes in acid balance.
Consistent with many chronic pain syndromes, changes may also occur at the level of the spinal cord and brain, which is one of the reasons chronic pain syndromes can be so challenging to treat. Not only is the nervous system capable of sprouting new sensory neurons creating unique pain referral patterns and changes in functional connectivity, but the brain is also critical in modulating our response to pain. Currently, the rostroventral medulla (RVM) has been receiving significant attention for its possible role in muscle pain.
Long Story Short...
What do you need to know? MPS may be common, but it is still a relatively poorly understood pain phenomenon. Be wary of providers who dismiss current pain theories and therapeutic treatments. Just because we don’t fully understand why the pain exists, doesn’t mean your pain doesn’t exist. At the same time, be open-minded to all types of treatment interventions- what works for one person might not work for another. Keep searching for what works for you!
What Treatments are Available?
The mainstay of treatment remains conservative therapy with exercise, heat, spray and stretch technique, acupressure, massage therapy, and medication management. More invasive interventions like acupuncture, dry needling, and/or trigger point injection (TPI) with local anesthetics, corticosteroids, and/or botulinum toxin are typically reserved for individuals who fail conservative treatment. Current research studies demonstrate inconsistent benefits for dry needling and TPI.
- Trigger point injections
- Dry Needling
- Spray and stretch
- Episodic tension headaches
- Temporomandibular disorder
- Muscle cramps
- Delayed onset muscle soreness
- Low back pain
Fernandez-de-Las-Penas, C.,Dommerholt, J. International Consensus on Diagnostic Criteria and Clinical Considerations of Myofascial Trigger Points: A Delphi Study. Pain Med 2018;19:142-150.
Shah, J.P., Thaker, N., Heimur, J., Aredo, J.V., Sikdar, S., Gerber, L. Myofascial Trigger Points Then and Now: A Historical and Scientific Perspective. PM R 2015;7:746-761.
Tekin, L., Akarsu, S., Durmus, O., Cakar, E., Dincer, U., Kiralp, M.Z. The effect of dry needling in the treatment of myofascial pain syndrome: a randomized double-blinded placebo-controlled trial. Clin Rheumatol 2013;32:309-315.
Gregory, N.S., Whitley, P.E., Sluka, K.A. Effect of Intramuscular Protons, Lactate, and ATP on Muscle Hyperalgesia in Rats. PLoS One 2015;10:e0138576.
Da Silva, L.F., Walder, R.Y., Davidson, B.L., Wilson, S.P., Sluka, K.A. Changes in expression of NMDA-NR1 receptor subunits in the rostral ventromedial medulla modulate pain behaviors. Pain 2010;151:155-161.